Engine blower

ABSTRACT

An engine blower is achieved which can obtain a large blowing volume and a high cooling efficiency of the cylinder and the muffler. A suction opening is formed in the second case partitioning the volute chamber and the muffler chamber at the front of the partition plate and at the rear of the muffler cover. The volute chamber has a shape that the width perpendicular to the front-rear direction is locally narrowed behind the suction opening, and a first curved portion is provided immediately after the suction opening, and a first curved portion is provided in the second case. Immediately before the first curved portion, the air pressure locally drops due to the air supply flow whose flow velocity is increased. The air pressure becomes a negative pressure state when viewed from the muffler chamber. Air flows from the muffler chamber side to the volute chamber side via the suction opening.

BACKGROUND Technical Field

The present invention relates to a structure of an engine blower poweredby an engine.

Description of Related Art

Among the blowers for generating and blowing wind, an engine blower inwhich an engine is used as a power source is effective because the windpower can be particularly increased. In particular, when a small engineis used, the engine blower can be portable, and the operator can holdthe engine blower and blow the air to a desired location. As a result,for example, dust on the road surface can be removed.

The configuration of such an engine blower is described in, for example,Patent Document 1. In this engine blower, a small air-cooled engine isused as a power source. The drive shaft of the engine is fixed with ablower fan for generating air emitted from the nozzles and a cooling fanfor generating cooling air for cooling the engine itself. The air flowgenerated by the fan is emitted from its tip via an elongate nozzle. Onthe other hand, the cooling air generated by the cooling fan cools thecylinder and the muffler of the engine, and then is discharged to theoutside. By directing the nozzle to a desired location, the operator canblow an air supply flow emitted from the tip thereof.

PRIOR ART DOCUMENT Patent Document

Patent document 1: Japan Patent Laid-Open No. JP-A-2010-13937

SUMMARY Problem to be Solved by the Invention

As described above, in the blower in which the blower fan and thecooling fan are used together, the blower fan is larger in size, and bymaking the blower fan large in size, it is possible to increase theamount of blown air emitted from the nozzles. However, when the blowerfan is large in size, it is difficult to increase the cooling efficiencyof the cylinder and the muffler because it is difficult to increase thesize of the cooling fan.

Further, it is also possible to cool the cylinder or the muffler byusing a part of the air supply flow generated by the air supply fan.However, in this case, the blowing amount of the blowing air flowemitted from the nozzle is lowered. Further, it is the cylinder and themuffler that are cooled by the cooling air, and in order to cool themtogether, the path of the cooling air becomes complicated, and it isdifficult to efficiently cool both of them.

That is, a blower which can obtain a large blowing amount and a highcooling efficiency of the cylinder and the muffler is desired.

The present invention has been made in view of the above problems, andan object thereof is to provide an invention which solves the aboveproblems.

In order to solve the above-mentioned problems, the present inventionhas the following configurations. The engine blower of the presentinvention comprises: an engine serving as a power source; a mufflermounted on the cylinder in front of the cylinder of the engine fordischarging exhaust gas from the cylinder; a muffler cover covering themuffler and forming a muffler chamber in which the muffler isaccommodated; a blower fan for generating a blown air flow emittedforward in a volute chamber by rotation of a drive shaft of the engine;a cooling fan for generating a cooling air for cooling the cylinder byrotation of the drive shaft; negative pressure generating means providedin the volute chamber for generating a negative pressure by the flow ofthe blown air flow; a partition wall for partitioning between thecylinder chamber in which the cylinder is accommodated; and an openingfor passing the muffler chamber and the volume chamber forward of thepartition wall for passing an air flow from the volume chamber to thevolume chamber by suction side. The engine blower of the presentinvention includes a case that covers the blower fan and constitutes thevolute chamber, and the negative pressure generating means is a firstcurved portion that is curved in the case so that the width of the airpath along the front-rear direction of the case becomes wider toward thefront, and the suction opening is located in front of the first curvedportion. The engine blower of the present invention is characterized inthat a second curved portion having a curved shape is provided behindthe first curved portion in the case so that the width of the air pathbecomes wider toward the rear. In the engine blower of the presentinvention, the blower fan is a centrifugal fan that flows the blowerflow from the rotational axis side in the volute chamber. In the engineblower of the present invention, the first curved portion is locatedoutside the blower fan when viewed from the rotation axis. In the engineblower of the present invention, the suction opening is located outsidethe blower fan when viewed from the rotation axis. In the engine blowerof the present invention, the air supply flow is configured to beemitted forward from a cylindrical nozzle whose inside communicates withthe volute chamber, and the suction opening is located on the side ofthe rotation axis side of the center axis of the nozzle. In the engineblower of the present invention, an opening for cooling the muffler andallowing cooling air flowing through the suction opening to pass towardthe muffler chamber side is provided in the front surface of the mufflercover.

Effect of the Invention

Since the present invention is configured as described above, it ispossible to obtain a blower which can obtain a large blowing amount anda high cooling efficiency of the cylinder and the muffler.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an engine blower according to an embodiment ofthe present invention.

FIG. 2 is a cross-sectional view in the direction A-A in the engineblower according to the embodiment of the present invention.

FIG. 3 is a side view of the engine blower according to the embodimentof the present invention in a state in which the first case and the fancover are removed;

FIG. 4 is a cross-sectional view in the B-B direction in the engineblower according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view in the C-C direction in the engineblower according to the embodiment of the present invention.

FIG. 6 is a diagram showing a flow of air between a volute chamber and amuffler chamber in an engine blower according to an embodiment of thepresent invention.

DESCRIPTION OF THE EMBODIMENTS

The structure of an engine blower according to an embodiment of thepresent invention will be described. In this engine blower, an engine(air-cooled engine) is used as a power source. As the drive shaft(crankshaft) of the engine rotates, an air flow emitted from the nozzlewith a large air flow rate and cooling air for cooling the cylinders ofthe engine are generated. The cooling air is also used to cool themuffler, but in addition, an air flow generated by a negative pressuregenerated when the feed air flow flows in the volute chamber is alsoused to cool the muffler. At this time, since it is suppressed that theflow rate of the air supply flow decreases in order to cool the muffler,the air supply amount of the air supply flow can be increased, and thecooling efficiency of the cylinder and the muffler can also beincreased.

FIG. 1 is a side view of this blower (engine blower) 1, and FIG. 2 is across-sectional view in the direction A-A thereof. When the blower 1 isactually used, the operator grasps the handle 11 provided at the upperportion in FIG. 1, and is positioned on the left side of the blower 1,that is, on the front side of the drawing in FIG. 1. The air flow isemitted toward the left side (front) from a nozzle (not shown) mountedvia a nozzle mounting portion 45 on the left side (front) in FIG. 1. Thestrength or ON/OFF of the air supply flow is controlled by operating atrigger lever 13 provided at the lower portion of the handle 11. In FIG.1, a side view along the drive axis of the engine used is shown from theleft as seen from the operator side.

In FIG. 2, a cross section along the drive shaft 21 of the engine 20used here and a cross section perpendicular to the intake and exhaustdirections thereof are shown, and this cross section is seen from therear side. In the engine 20, a cylinder 24 in which a piston 23 fordriving the drive shaft 21 slides in the vertical direction is providedin an upper portion of a crankcase 22 in which the drive shaft 21 isaccommodated. The engine 20 is an air-cooled type, and a plurality ofplate-like cooling fins 24 A extending in the horizontal direction areformed around the cylinder 24 side by side in the vertical direction,and cooling air mainly flows between the cooling fins 24 A to cool thecylinder 24 which generates heat during operation.

A starting device 25 is mounted on the right side of the drive shaft 21,and by forcibly rotating the drive shaft 21 by the starting device 25,fuel supplied from a fuel tank 26 provided on the lower side of thecrankcase 22 is guided to the engine 20 side, and the engine 20 can bestarted. When the drive shaft 21 rotates, electric power generated by apower generating coil (not shown) is supplied to an ignition plug (notshown in FIG. 2) mounted on the cylinder 24 via the ignition device 27.

On the left side of the drive shaft 21, a cooling fan 31 and a blowerfan 32 having a diameter larger than that of the cooling fan 31 aresuccessively fixed from the side close to the crankcase 22. In FIG. 2, afirst case (case) 41, a second case (case) 42, and a third case (case)43 made of resin are combined to form a cylinder chamber 40 A, which isa space in which the cylinder 24 and the cooling fan 31 are built, and avolute chamber 40 B, which is a space in which the blower fan 32 isbuilt, respectively. The cooling air CA generated by the cooling fan 31flows through the cylinder chamber 40 A as indicated by arrows in FIG.2, thereby cooling the cylinder 24.

The blower fan 32 is covered with a fan cover 44 from the left side, anda large number of openings 44 A are formed in the fan cover 44. Theblower fan 32 is a centrifugal fan that generates a blowing air flow byflowing outside air sucked from the opening 44 A along the outercircumferential direction from the side of the rotation axis, i.e., theaxis of the drive shaft 21. This air supply flow flows through thevolute chamber 40 B.

FIG. 3 shows a configuration in which the first case 41 and the fancover 44 are removed in the configuration of FIG. 1, and shows the flowof the air supply flow W in the volute chamber 40 B. Here, it is assumedthat the blower fan 32 is driven to rotate counterclockwise. In FIG. 1,a nozzle mounting portion 45 is formed by combining a first case 41 anda second case 42, and a long cylindrical nozzle (not shown) is mountedon the nozzle mounting portion 45. The central axis of the nozzle andnozzle mounting portion 45 is shown as X in FIG. 3. In FIG. 3, the airsupply flow W flows counterclockwise in the volute chamber 40 B, andthen is emitted forward from the nozzle through the nozzle mountingportion 45.

FIG. 4 is a cross-sectional view taken along the B-B direction in FIGS.1 and 3, and shows a case in which the first case 41 and the fan cover44 are also mounted. In this figure, a structure is shown in which across section of the engine 20 along the intake/exhaust direction isviewed from the upper side. FIG. 5 is a cross-sectional view taken alongthe C-C direction in FIG. 4, and here, a structure in which across-section taken along the intake/exhaust direction is viewed fromthe right side is shown. In FIGS. 4 and 5, a carburetor 51 is connectedto the rear of the cylinder 24 via an intake pipe 28, and an air cleaner52 is connected to the rear of the carburetor 51. In the carburetor 51,an air-fuel mixture is formed by the air introduced through the aircleaner 52 and the fuel supplied from the fuel tank 26, and is suppliedto the engine 20 (crankcase 22) through the intake port 24 B on thecylinder 24 side. In the cylinder 24, the air-fuel mixture is compressedand ignited by an upper spark plug 29, thereby operating the engine 20.

On the other hand, a muffler 53 for passing exhaust gas discharged fromthe exhaust port 24 C on the cylinder 24 side at this time is connectedto the front of the cylinder 24. The exhaust gas passes through thecatalyst inside the muffler 53 and is then discharged toward the outsideair. By the catalytic reaction at this time, the muffler 53 alsogenerates heat in the same manner as the cylinder 24 during theoperation. The muffler 53 is covered with a resin muffler cover 46 fromthe front. Between the cylinder 24 and the muffler 53, a plate-likepartition plate 54 extending perpendicularly to the plane of the drawingin FIGS. 4 and 5 is provided. The muffler cover 46 is combined with orintegrated with the second case 42, the third case 43, and the like, anda partition plate 54 is further provided to form a muffler chamber 40 Cin which the muffler 53 is accommodated. However, the partition plate 54does not exist on the right side (left side in FIG. 4) of the cylinder24 and the muffler 53, and this portion becomes the communicationpassage 40 D that connects the cylinder chamber 40 A and the mufflerchamber 40 C, and the cooling air CA can flow from the cylinder chamber40 A to the muffler chamber 40 C through this communication passage 40D. A plurality of small openings 46 A is provided in front of themuffler cover 46, and the muffler chamber 40 C communicates with thefront outside air through the openings 46 A.

FIG. 6 is a diagram showing the flow of air during operation in FIG. 4.The cooling air CA shown in FIG. 2 is roughly divided into a cooling airCA1 flowing behind the cylinder 24 and a cooling air CA2 flowing infront of the cylinder 24 in a top view as shown in FIG. 6. The coolingair CA1 and the cooling air CA2 both pass through the communicationpassage 40 D and are discharged forward. At this time, the right sidesurface of the muffler 53 is cooled by these. However, in the muffler53, the cooling air CA1 and the cooling air CA2 are in contact only withthe right side surface thereof, and in this condition, the cooling airCA1 and the cooling air CA2 after the cylinder 24 is cooled and thetemperatures are raised are in contact with the muffler 53, so that thecooling air CA1 and the cooling efficiency of the muffler 53 by the CA2are not high.

In FIG. 6, the air supply flow W generated by the blower fan 32 flows inthe volute chamber 40 B from the rear toward the front, and the flowrate thereof is larger than the cooling air CA1 and the cooling air CA2,as described above. Since the second case 42 exists between the volutechamber 40 B and the adjoining cylinder chamber 40 A and the mufflerchamber 40 C, and the cylinder chamber 40 A and the volute chamber 40 Bare partitioned by the second case 42, the air supply flow W, thecooling air CA1, and the cooling air CA2 do not flow between thecylinder chamber 40 A and the volute chamber 40 B.

On the other hand, in the second case 42 that partitions the volutechamber 40 B and the muffler chamber 40 C, an opening (suction opening42 A) is formed in the front of the partition plate 54 and in the rearof the muffler cover 46. Therefore, there may be a flow of air betweenthe volute chamber 40 B and the muffler chamber 40 C through the suctionopening 42 A.

Here, as shown in FIGS. 4 and 6, the volute chamber 40 B has a shapesuch that a width (air path width) perpendicular to the front-reardirection is locally narrowed behind the suction opening 42 A (upstreamside in the flow direction of the air supply flow W). Specifically,immediately after the suction opening 42 A, a portion (first curvedportion 41 B) that curves rightward (leftward in the figure) from thefront to the rear in the first case 41 is provided, and a portion (firstcurved portion 42 B) that curves leftward (rightward in the figure) fromthe front to the rear in the second case 42. In addition, a portion(second curved portion 41 C) that curves leftward from the front to therear is provided at the rear of the first curved portion 41 B in thefirst case 41, and a portion (second curved portion 42 C) that curvesrightward from the front to the rear is provided at the rear of thefirst curved portion 42 B in the second case 42. By providing the firstcurved portions 41 B, 42 B and the second curved portions 41 C, 42 C,the air flow path of the air flow W is locally narrowed between thefirst curved portions 41 B, 42 B and the second curved portions 41 C, 42C, and the flow velocity of the air flow W is locally increased in thisportion. Further, in the second case 42, since the suction opening 42 Ais located forward of the first curved portion 41 B and on thedownstream side in the flow direction of the air supply flow W, the airsupply flow W whose flow speed is increased and the suction opening 42 Aare separated from each other, and the inflow of the air supply flow Winto the muffler chamber 40 C through the suction opening 42 issuppressed.

However, the air pressure locally decreases immediately before the firstcurved portion 42 B (immediately after the flow of the air flow W) dueto the air flow W whose flow velocity is increased, and the air pressurebecomes a negative pressure state when viewed from the muffler chamber40 C. Therefore, air flows from the muffler chamber 40 C side to thevolute chamber 40 B side via the suction opening 42 A. This air issupplied mainly through an opening 46 A in front of the muffler cover46. Therefore, the cooling air CA3 shown in FIG. 6 flows through thesuction opening 42 A. Since this cooled air CA3 is generated from theoutside air through the front opening 46 A, the temperature in contactwith the muffler 53 in the muffler chamber 40 C is room temperature. Ifa plurality of the openings 46 A is formed in a wide range on the frontsurface of the muffler cover 46, the cooling air CA3 can flow in a widerange in the left and right directions of the muffler 53. Therefore, theefficiency of cooling the muffler 53 by the cooling air CA3 can beincreased. At this time, as described above, the cooling air CA1 and CA2flowed forward at the right end portion of the muffler chamber 40 C,while the cooling air CA3 flowed rearward through the muffler cover 46(opening 46 A).

Further, the muffler cover 46 is also cooled by the cooling air CA3.Therefore, it is possible to use a material having low heat resistanceas a material constituting the muffler cover 46.

The cooling air CA3 is generated by the negative pressure generated inthe volute chamber 40 B, and after flowing into the volute chamber 40 B,the cooling air joins the air supply flow W and is finally emittedforward from the nozzles. Therefore, the flow rate of the air supplyflow W is not impaired by the generation of the cool air CA3. Inaddition, although the temperature of the cooling air CA3 after coolingthe muffler 53 rises, the flow rate of the air supply flow W generatedby the blower fan 32 is large, so that the temperature rise of the airsupply flow W finally emitted from the nozzles is slight. For thisreason, in the blower 1, a large amount of blown air flow W is obtained,and high cooling efficiency of the cylinder 24 and the muffler 53 isobtained.

Here, in FIG. 3, the positional relationship among the suction opening42 A, the first curved portion 42 B, the second curved portion 42 C, andthe blower fan 32 is shown. As described above, the blower fan 32 is acentrifugal fan, so that the generated air flow W flows counterclockwisein FIG. 3 and then forward along the upper surface of the volute chamber40 B along the front and backward direction. It is preferable togenerate a large negative pressure in the volute chamber 40 B at alocation of the suction opening 42 A. Therefore, it is preferable toprovide the suction opening 42 A at a position where the flow velocityof the air supply flow W is highest in this configuration, and it ispreferable to form the suction opening 42 A outside the blower fan 32 asviewed from the rotation axis side of the blower fan 32 (the axis of thedrive shaft 21) in FIG. 3. However, the flow velocity of the air supplyflow W decreases as it approaches the upper surface of the volutechamber 40 B with a large distance from the rotation axis. Therefore, itis preferable to provide the suction opening 42 A below the center axisX of the nozzle in FIG. 3.

In order to increase the effect of forming the negative pressure, it ispreferable to provide the first curved portion 42 B 41 B at a placewhere the flow velocity of the air supply flow W is high. Therefore, itis preferable that the first curved portion 42 B 41 B is also formedoutside the blower fan 32.

By providing the second curved portion 42 C (41 C) together with thefirst curved portion 42 B (41 B), it is possible to form a region inwhich the flow velocity of the air supply flow W is locally increased inthe front-rear direction. However, when the flow velocity of the airsupply flow W generated by the blower fan 32 is high, a negativepressure is generated at a point where the width perpendicular to theflow direction rapidly widens. Therefore, in such a case, the negativepressure can be generated downstream of the first curved portion byproviding only the first curved portion without forming the secondcurved portion on the upstream side with respect to the flow.

In the above example, the first curved portions 42 B, 41 B and thesecond curved portions 42 C, 41 C are used as negative pressuregenerating means for generating a negative pressure by the flow of theair supply flow W in the volute chamber 40 B. However, otherconfigurations in the first case, the second case, or other componentsseparate therefrom may be used to generate the negative pressure aswell. Even in such a case, by providing the suction opening at aposition where the negative pressure is generated, that is, a positionimmediately after the position where the negative pressure generatingmeans is provided in the flow of the air supply flow, the cooling aircan be flowed in the muffler chamber in the same manner.

REFERENCE SIGNS LIST

1 . . . Blower (Engine Blower), 11 . . . Handle, 13 . . . Trigger(Trigger Lever), 20 . . . Engine, 21 . . . Drive shaft (Crankshaft), 22. . . Crankcase, 23 . . . Piston, 24 . . . Cylinder, 24A . . . Inlet,24B . . . Inlet, 24C . . . Exhaust, 25 . . . Starter, 26 . . . FuelTank, 27 . . . Igniter, 28 . . . Intake pipe, 29 . . . Ignition plug, 31. . . Cooling fan, 32 . . . Blower fan, 40 A . . . Cylinder, 40B . . .Volute chamber, 40C . . . Muffler chamber, 40D . . . Communicationpassage, 41 . . . First case, 41B, 42B . . . First curved portion, 41C,42C . . . Second curved portion, 42 . . . Second case, 42A . . . suctionopening, 43 . . . third case, 44 . . . fan cover, 44A, 46A . . .opening, 45 . . . nozzle mounting portion, 46 . . . muffler cover, 51 .. . carburetor, 52 . . . air cleaner, 53 . . . muffler, 54 . . .partition plate, CA, CA1, CA, CA2, and CA3 . . . cooling air, W . . .air supply flow, X . . . center shaft

1. An engine blower comprising: an engine serving as a power source; amuffler mounted to a cylinder of the engine and in front of the cylinderfor causing exhaust gas from the cylinder to pass and discharge; amuffler cover covering the muffler and forming a muffler chamber inwhich accommodate the muffler; a blower fan for generating a blown airflow emitted forward in a volute chamber by rotation of a drive shaft ofthe engine; a cooling fan for generating a cooling air for cooling thecylinder by the rotation of the drive shaft; a negative pressuregenerating device provided in the volute chamber for generating anegative pressure by a flow of the blown air; a partition wall forpartitioning the muffler chamber and a cylinder chamber thataccommodates the cylinder; and a suction opening communicating themuffler chamber and the cylinder chamber in front of the partition walland causing air flow from a side of the muffler chamber to a side of thecylinder chamber to pass by the negative pressure.
 2. The engine bloweraccording to claim 1, further comprising a case covering the blower fanand constituting the volute chamber, wherein the negative pressuregenerating means is a first curved portion curved in the case so thatthe width of the air path along the front-rear direction of the casebecomes wider toward the front, and the suction opening is located infront of the first curved portion.
 3. The engine blower according toclaim 2, a second curved portion having curved shape such that the widthof the air path widens rearward is provided behind the first curvedportion in the case.
 4. The engine blower according to claim 2, theblower fan is a centrifugal fan that generates the blown air from therotational axis side in the volute chamber.
 5. The engine bloweraccording to claim 4, the first curved portion is located an outside theblower fan when viewed from the rotation axis.
 6. The engine bloweraccording to claim 4, wherein the suction opening is located an outsidethe blower fan when viewed from the rotation axis.
 7. The engine bloweraccording to claim 4, wherein the blown air flow is emitted forward froma cylindrical nozzle whose inside communicates with the volute chamber,and the suction opening is located closer to the center of the rotationaxis than the center axis of the cylindrical nozzle.
 8. The engineblower according to claim 1, wherein a front surface of the mufflercover is provided with an opening for passing cooling air flows throughthe suction opening toward the muffler chamber side to cool the muffler.9. The engine blower according to claim 3, the blower fan is acentrifugal fan that generates the blown air from the rotational axisside in the volute chamber.
 10. The engine blower according to claim 9,the first curved portion is located an outside the blower fan whenviewed from the rotation axis.
 11. The engine blower according to claim10, wherein the suction opening is located an outside the blower fanwhen viewed from the rotation axis.
 12. The engine blower according toclaim 10, wherein the blown air flow is emitted forward from acylindrical nozzle whose inside communicates with the volute chamber,and the suction opening is located closer to the center of the rotationaxis than the center axis of the cylindrical nozzle.
 13. The engineblower according to claim 11, wherein the blown air flow is emittedforward from a cylindrical nozzle whose inside communicates with thevolute chamber, and the suction opening is located closer to the centerof the rotation axis than the center axis of the cylindrical nozzle. 14.The engine blower according to claim 2, wherein a front surface of themuffler cover is provided with an opening for passing cooling air flowsthrough the suction opening toward the muffler chamber side to cool themuffler.
 15. The engine blower according to claim 3, wherein a frontsurface of the muffler cover is provided with an opening for passingcooling air flows through the suction opening toward the muffler chamberside to cool the muffler.